In the prior art, windshield wipers have been made that include a blade which is moved over the surface to be swept, for example a windshield, under the action of a motor. Such windshield wipers include at least one oscillating arm which carries a blade that includes a wiping strip. The wiping strip generally comprises a base and a scraping or wiping element. The wiping strip is carried by the blade which is articulated on the arm, with the latter applying the blade firmly against the swept surface while moving it in an oscillating movement.
In order to overcome problems of mechanical behaviour, for example noisiness, it is known to articulate the base on the wiping element itself by interposing a web between these two portions of the wiping strip. Such a web may be defined by one or more cavities formed along the wiping strip.
Such arrangements have deceptive aerodynamic behaviour, in particular at high speeds. Under the effect of eddies of air, lateral overpressures tend to occur, which cause the wiping strip to undergo a constraint which tends to oppose the required angular deformation about the web.
In addition, such an overpressure can induce a braking effect in the movements of the windshield wiper blade: this needs to be avoided, for example under high-stress driving conditions in a high speed vehicle.
Another problem has become apparent under certain wiping conditions. Thus, when the blade sweeps the surface of the windshield, it often happens that the region around the web can become clogged by accumulations of foreign matter, for example, ice or mud comprising a mixture of dust and water. This reduces the ability of the strip to flex at the web, which is damaging both to performance and to the structure of the strip. In addition, such accumulations of matter can be transferred onto the windshield.
In French patent No. 1 250 889, a wiping strip has been proposed which is protected from the surrounding air, since it is disposed within a mask in the form of a channel or gutter carried by the windshield wiper arm itself. The main drawback of that arrangement is that ingress of dust and accumulation of ice during snowfall are not in fact prevented, for example between the channel and the wiping strip itself. It is therefore possible to reach a point at which the channel is full of dust and ice and the wiping strip is therefore unable to function properly. In addition, the channel is a supplementary component of a windshield wiper, which adds to the cost of the wiper assembly.
In the solution of another problem that has been proposed in the prior art, it is known to arrange for the wiping strip to be stiffened in such a way that the windshield wiper remains permanently in contact over its whole length with the swept surface. With this in view, the upper part of the base, i.e. the part opposite the web, is formed with a recess or cavity in which a vertebra or stiffener can be fitted. This arrangement increases the risks of braking of the windshield wiper blade and, more particularly, of clogging by mud or ice.